Carburetor

ABSTRACT

In an air valve carburetor, a reciprocable plunger controls the linkage between the air valve and the metering rod to vary the air-fuel ratio. The plunger is positioned by a vacuum unit, and its limits of travel are controlled by stops which are accessible for adjustment only by removing the vacuum unit.

United States Patent 11 1 Gural et al. June 3, 1975 [54] CARBURETOR 3,263,974 8/1966 Braun et al. 261/50 A 75 Inventors: John A. Gural, Pittsford; John w. """f: 2 Mmlds, Penfield, both of 3,677,241 7/1972 Gele et al. 261/50 A A ig General Motors Corporation, 3,807,710 4/1974 Bergammi 261/39 A Detroit, Mich. Primary ExaminerTim R. Miles [22] Flled: 1974 Attorney, Agent, or Firm-C. K. Veenstra [21] Appl. No.: 447,586

[57] ABSTRACT [52] us. Cl. 261/39 A; 261/50 A In an air valve carburetor, a reeiproeable pl ng r n- [51] Int. Cl. F02m 7/22 trols h ink g een he air valve and the meter- [58] Field of Search 261/39 A, 50 A ng rod to y he ir-f l ratio. The plunger is positioned by a vacuum unit, and its limits of travel are [56] Refer Cit d controlled by stops which are accessible for adjust- UNITED STATES PATENTS ment only by removing the vacuum unit.

3,053,240 9/1962 Mick 261/50 A 2 Claims, 4 Drawing Figures :59 w 62 w I? 50 y 55 #9110 a 58 26 m: 161 W 52 i (If z 2?: O I 5g 98 w 22 38 w 28 5; i0 1 [531 3? x .53 5 \z a;

1 Q 9 l0 10 1 zz 1 I476 43 i| J 31 I8 3 SHEET PATENTED 3 PATENTED 3 SHEET CARBURETOR This invention relates to a carburetor for an internal combustion engine and more particularly to such a carburetor having a novel mechanism for adjusting the airfuel ratio delivered to the engine.

Carburetors are conventionally provided with a manifold vacuum responsive device which limits fuel flow during high vacuum conditions to provide a lean airfuel mixture for economy operation and which permits increased fuel flow during low vacuum conditions to provide an enriched air-fuel mixture for power operation. In some instances, adjustable stops have been proposed for variably limiting travel of the vacuum responsive device and thereby adjusting the economy and power mixture ratios.

This invention provides a carburetor having a novel mixture ratio adjustment mechanism which variably limits travel of a reciprocable plunger operated by a vacuum unit. In this mechanism, economy and power mixture ratio adjustments are disposed concentrically for compactness and adaptability to computer controlled adjusting mechanisms. Further, the adjustments are accessible only by removing the vacuum unit to inhibit tampering by unqualified personnel. With this invention, therefore, carburetor mixture ratios may be accurately set at the factory and secured against tampering and yet may be easily adjusted by qualified personnel if necessary.

'The details as well as other objects and advantages of this invention are set forth in the remainder of the specification are shown in the drawings in which:

FIG. 1 is a sectional elevational view of an air valve carburetor embodying the novel adjustment mechanism;

FIG. 2 is a view of a portion of FIG. 1 enlarged to show details of the mixture ratio adjustments;

FIG. 3 is a view, taken in the direction indicated by line 3-3 of FIG. 2, showing a clip for retaining the vacuum unit, and

FIG. 4 is a sectional view, taken along line 4-4 of FIG. 3, further illustrating the'vacuum unit retaining pins and clip.

Referring first to FIG. 1, the carburetor has a mixture conduit 12 including an air inlet 14 and a mixture outlet 16 which discharges to the engine. A throttle 18 is disposed in mixture outlet 16 in the usual manner on a throttle shaft 20.

An air valve 22 is disposed in air inlet 14 on an air valve shaft 24. A spring 26 is secured to the downstream edge 28 of air valve 22 and extends to a bracket 30 to bias air valve 22 to the position shown.

A tang 32 reaches upwardly from air valve 22 and is connected by a link 34 to a diaphragm 36. A chamber 38, formed between the right side of the diaphragm 36 and a cover member 40, is connected by a tube 42 to a region 44 of mixture conduit 12 defined between air valve 22 and throttle 18.

A chamber 46, defined between the left side of diaphragm 36 and a cover member 48, is subjected to substantially atmospheric pressure, present in air inlet 14 and in the air cleaner (not shown), through openings such as 50, 51 and 52. (The air cleaner seats on a rim 53 disposed about the upper portion of carburetor 10.) Cover member 48 is welded to a bracket 54 which is secured to the air horn 55, and a grommet 56 is disposed between bracket 54 and air horn 55.

In operation, chamber 38 is subjected to the subatmospheric pressure created in region 44 as throttle 18 is opened, and diaphragm 36 acts through link 34 to pull air valve 22 clockwise to an open position. Spring 26 is effective to balance the opening force of diaphragm 36, thereby creating a substantially constant subatmospheric pressure in region 44. By thus establishing a generally constant pressure drop across air valve 22, the area about air valve 22 and thus the rotative position of air valve 22 is determined by and is a measure of the rate of air flow through mixture conduit 12.

A tab 58 extends upwardly from air valve 22 and is connected through a link 60 to one end 62 of a lever 64. The opposite end 66 of lever 64 is pivoted about a pin 68. Intermediate ends 62 and 66, a hanger 70 extends from lever 64 into the carburetor fuel bowl 72. The lower end 74 of hanger 70 has a hook 76 which is received in a recess 78 formed in a metering rod 80.

It may be noted that hanger 70 extends through an opening 82 in the fuel bowl cover portion 84 of air horn 55. Opening 82 is closed by a slider 86 which shifts horizontally during movement of hanger 70.

Metering rod is disposed in a fuel passage 88 having its lower end 90 disposed to receive fuel from a well 92 formed in the bottom of fuel bowl 72. The upper end 94 of fuel passage 88 has an opening 96 through which fuel is discharged into region 44 of mixture conduit 12. It will be appreciated, therefore, that the fuel in fuel bowl 72 is subjected to a substantially constant metering head from the substantially atmospheric pressure in the upper portion of the fuel bowl to the generally constant pressure in region 44.

A metering jet or orifice 98 is disposed in fuel passage 88 around the tip 99 of metering rod 80. Metering rod 80 has flat tapered surfaces 100 on opposite sides which, upon reciprocationof metering rod 80 in jet 98, varies the area available for fuel flow through jet 98.

In operation, as air valve 22 opens by clockwise rotation, link 60 rotates lever 64 in a clockwise direction. Lever 64 then lifts hanger 70 to move metering rod 80 generally upwardly and rightwardly in fuel passage 88. Thus as air valve 22 is opened to increase the area available for air flow through air inlet 14, metering rod 80 is shifted to increase the area available for fuel flow through metering orifice 98. By this means, a substantially constant air-fuel ratio may be maintained the precise proportion being controlled by the geometry of tapered surfaces 100 and of the linkage between air valve 22 and metering rod 80.

A spring 102 extends from a ledge 104 formed in fuel passage 88 to the lower end 106 of metering rod 80 to take up any slack in the linkage and to load metering rod 80 against jet 98.

It may be noted that the thickness of metering rod 88 increases from the end of surfaces 100 closely adjacent passage inlet 90 to tip 99. Tip 99 is therefore enlarged and assists in discharging fuel from fuel passage 88 as air valve 22 and metering "rod 80 are moved to increase air and fuel flow. This offsets the greater inertia of the fuel which otherwise could create a mixture temporarily leaner than desired.

A slot 108 is formed in the end 62 of lever 64. Link 60 is connected to lever 64 by having one end 110 disposed in slot 108. A link 112 extends from the end 110 of link 60 to arm 114 of a supplementary lever l 16 pivoted at 118. The opposite am of lever 116 is connected by a link 122 to one end 124 of an aneroid or bellows 126. As shown in enlarged detail in FIG. 2, the opposite end 128 of aneroid 126 is connected to a rc ciprocable plunger 130 slidingly received in a ferrule 131 and abutting a threaded economy adjusting screw 132 carried ferrule 131. (In some embodiments, plunger 130 and screw 132 may be integral.) Ferrule 131 is guided in the bore 134 of an adjustable power stop 136 and has a tail 137 engaging a diaphragm 138 of a vacuum unit 139.

A chamber 140 defined between the right side of diaphragm 138 and a cover member 142 is subjected to the manifold vacuum in mixture outlet 16 downstream of throttle 18, while a chamber 144 defined between the left side of diaphragm 138 and a cover member 147 is subjected to atmospheric pressure. The resulting rightward bias on diaphragm 138 is resisted by a spring 148 disposed between the head 149 of ferrule 131 and an economy stop 150.

When manifold vacuum increases to a point indicative of a need for a lean or economy air-fuel ratio, diaphragm 138 forces ferrule 131 and plunger 130 rightwardly until the nose 151 of ferrule 131 engages stop 150. This forces aneroid 126 and link 122 rightwardly resulting in clockwise rotation of lever 116. Lever 116 then lifts link 112 to raise the end 110 of link 60 in slot 108 and increase the lever arm defined between link end 110 and pivot pin 68. This reduces the travel of metering rod 80 through metering jet 98 for equivalent opening movement of air valve 22 to provide a lean airfuel mixture.

When throttle 18 is opened and manifold vacuum drops to a point indicative of the need for an enriched or power air-fuel ratio, spring 148 moves ferrule 131 leftwardly until head 149 engages the face 152 of stop 136. Link 130 is thus freed for leftward movement and a spring 153, entending between end 120 of supplementary lever 116 and a support 154, moves supplementary lever 116 counterclockwise to move link 122, aneroid 126 and plunger 130 leftwardly. Simultaneously, lever 116 pulls link 112 downwardly to lower the end 110 of link 60 in slot 108, thereby resulting in a shorter lever arm defined between link end 110 and pivot pin 68. This increases the travel of metering rod 80 through metering jet 98 for equivalent opening movement of air valve 22 to provide an enriched airfuel mixture.

Upon a decrease in ambient air pressure or an increase in ambient air temperature, both indicative of a reduction in air density and consequently a reduction in the mass rate of air flow through air inlet 114 for equivalent volume air flow, aneroid 126 expands forcing link 122 rightwardly and causing clockwise rotation of lever 116. Lever 116 moves link 112 to raise the end 110 oflink 60 in slot 108 and increase the lever arm defined between link end 110 and pivot pin 68. The increased lever arm reduces the travel of metering rod 80 in metering jet 98 for equivalent movement of air valve 22 to prevent air-fuel mixture enrichment caused by a reduction in air density.

Upon an increase in ambient air pressure or a decrease in ambient air temperature, both indicative of an increase in air density, aneroid 126 contracts. Spring 153 then causes counterclockwise rotation of supplementary lever 116 which pulls link 112 to move link end 110 downwardly in slot 108 and shorten the lever arm defined between end 110 and pivot pin 68. The

shortened lever arm increases the travel of metering rod in jet 98 for equivalent'movement of air valve 22 to prevent leaning of the air-fuel mixture due to an increase in air density. I I

'As shown in FIGS. 3 and 4, cover member 142 carriers a pair of retaining pins '156 which extend through the wall 158 of carburetor "10.. The inner ends 160 of pins 156 have annular grooves 162 which receive a retaining clip 164.

Clip 164 has a central portion 166 which spans ferrule 131 and stop 136 and a pair of bifurcated ends 168 which receive pins 156. As viewed in FIG. 3, each end 168 is bent concavely along lines 170 and 172 and convexly along line 174. When installed, the convexly bent portions 174 of clip 164 bear against the inner ends of 160 of pins 156 while the concavely bent portions 170 and 172 bear against wall 158. This retains vacuum motor 139 on air horn 55 and snugly secures a gasket 176 between cover member 142 and wall 158 to prevent air from leaking into chamber 140. If desired, gasket 176 may include a boot surrounding the head 178 of stop 136 and the tail 137 of ferrule 131. Alternatively, a seal may surround ferrule 131 within stop 136.

It will be noted that adjusting screw 132 and adjustable stop 136 are disposed to inhibit tampering by unqualified personnel. If adjustment of the power or economy mixture ratio is required, retaining clip 164 is pulled upwardly to free retaining pins 156 and vacuum unit 139 is pulled outwardly to expose screw 132 and stop 136.

To adjust the economy air-fuel ratio, a screwdriver is inserted in ferrule 131 to engage adjusting screw 132 and sufficient axial force applied to overcome the bias of spring 148 and engage nose 151 with stop 150. Screw 132 is then turned to move plunger 130 rightwardly against the bias of spring 153 for a leaner economy air-fuel mixture or leftwardly for a richer economy air-fuel mixture. Head 149 of ferrule 131 is adapted for retention by a wrench to permit turning of screw 132 within ferrule 131.

To adjust the power air-fuel ratio, head 149 of ferrule 131 is permitted to engage power stop 136. Stop head 178 is then engaged and turned by a wrench to move ferrule 131 and plunger 130 rightwardly against the bias of spring 153 for a leaner power air-fuel mixture or leftwardly for a richer power air-fuel ratio.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A carburetor comprising a mixture conduit having an air inlet and a mixture outlet, a throttle disposed in said mixture outlet for controlling flow therethrough, an air valve disposed in said air inlet for measuring air flow therethrough, a fuel passage entending to said mixture conduit for supplying fuel thereto, a metering orifice disposed in said fuel passage, a metering rod disposedin said metering orifice for controlling fuel flow therethrough, a lever positioning said metering rod, a link extending from said air valve to said lever for moving said lever and said metering rod to control fuel flow through said metering orifice in accordance with air flow through said air inlet, said lever having a slot receiving said link, and means'for varying the position of said link in said slot to vary the travel of said metering rod in said orifice for selected movement of said air valve, said means including a reciprocable plunger connected to said link, a ferrule surrounding said plunger,

said plunger having an adjusting screw received in one end of said ferrule for varying the relative positions of said plunger and said ferrule, a wall, an adjustable stop supported in said wall and surrounding said ferrule, said ferrule having a head engageable with one end of said adjustable stop, spring means biasing said head into engagement with said end of said adjustable stop, stop means engageable with the opposite end of said ferrule for limiting travel of said ferrule away from said adjustable stop against the bias of said spring means, a diaphragm engaging said one end of said ferrule and cover means surrounding said one end of said ferrule and the opposite end of said ferrule for limiting travel of said ferrule away from said adjustable stop against the bias of said spring means, a diaphragm engaging said one end of said ferrule and cover means surrounding said one end of said ferrule and the opposite end of adjustable stop and defining a chamber enclosed by said diaphragm and subjected to the pressure in said mixture conduit downstream of said throttle, whereby when said pressure is below a selected level said diaphragm may displace said ferrule and said plunger against the bias of said spring means to engage said ferrule with said stop means and to move said link in said slot to provide an enriched air-fuel mixture, whereby when said pressure is above said selected level said spring means may displace said ferrule, said diaphragm and said plunger to engage said ferrule head with said adjustable stop and to move said link in said slot to provide a lean air-fuel mixture, and whereby said air-fuel mixtures may be adjusted by removing said cover means and said diaphragm to expose said one end of said ferrule and said opposite end of said adjustable stop, by adjusting the position of said adjusting screw relative to said ferrule, and by adjusting the position of said adjustable stop relative to said wall.

2. A carburetor comprising a mixture conduit having an air inlet and a mixture outlet, at throttle disposed in said mixture outlet for controlling flow therethrough, an air valve disposed in said air inlet for measuring air flow therethrough, a fuel passage extending to said mixture conduit for supplying fuel thereto, a metering orifice disposed in said fuel passage, a metering rod disposed in said metering orifice for controlling fuel flow therethrough, a lever positioning said metering rod, a link extending from said air valve to said lever for moving said lever and said metering rod to control fuel flow through said metering orifice in accordance with air flow through said air inlet, said lever having a slot receiving said link, and means for varying the position of said link in said slot to vary the travel of said metering rod in said orifice for selected movement of said air valve, said means including a reciprocable plunger connected to said link, a ferrule surrounding said plunger, said plunger having an adjusting screw received in one end of said ferrule for varying the relative positions of said plunger and said ferrule, a wall, an adjustable stop supported in said wall and surrounding said ferrule, said ferrule having a head engageable with one end of said adjustable stop, spring means biasing said head into engagement with said end of said adjustable stop, stop means engageable with the opposite end of said ferrule for limiting travel of said ferrule away from said adjustable stop against the bias of said spring means, a diaphragm engaging said one end of said ferrule, cover means surrounding said one end of said ferrule and the opposite end of said adjustable stop and defining a chamber enclosed by said diaphragm and subjected to the pressure in said mixture conduit downstream of said throttle, said cover means engaging one side of said wall and having a retaining pin extending through said wall, and a retaining clip disposed on the opposite side of said wall and engaging said retaining pin to secure said cover means to said wall, whereby when said pressure is below a selected level said diaphragm may displace said ferrule and said plunger against the bias of said spring means to engage said ferrule with said stop means and to move said link in said slot to provide an enriched airfuel mixture, whereby when said pressure is above said selected level said spring means may displace said ferrule, said diaphragm and said plunger to engage said ferrule head with said adjustable stop to move said link in said slot to provide a lean air-fuel mixture, and whereby said air-fuel mixtures may be adjusted by removing said clip from said pin, by removing said cover means and said diaphragm to expose said one end of said ferrule and said opposite end of said adjustable stop, by adjusting the position of said adjusting screw relative to said ferrule, and by adjusting the position of said adjustable stop relative to said wall. 

1. A carburetor comprising a mixture conduit having an air inlet and a mixture outlet, a throttle disposed in said mixture outlet for controlling flow therethrough, an air valve disposed in said air inlet for measuring air flow therethrough, a fuel passage entending to said mixture conduit for supplying fuel thereto, a metering orifice disposed in said fuel passage, a metering rod disposed in said metering orifice for controlling fuel flow therethrough, a lever positioning said metering rod, a link extending from said air valve to said lever for moving said lever and said metering rod to control fuel flow through said metering orifice in accordance with air flow through said air inlet, said lever having a slot receiving said link, and means for varying the position of said link in said slot to vary the travel of said metering rod in said orifice for selected movement of said air valve, said means including a reciprocable plunger connected to said link, a ferrule surrounding said plunger, said plunger having an adjusting screw received in one end of said ferrule for varying the relative positions of said plunger and said ferrule, a wall, an adjustable stop supported in said wall and surrounding said ferrule, said ferrule having a head engageable with one end of said adjustable stop, spring means biasing said head into engagement with said end of said adjustable stop, stop means engageable with the opposite end of said ferrule for limiting travel of said ferrule away from said adjustable stop against the bias of said spring means, a diaphragm engaging said one end of said ferrule and cover means surrounding said one end of said ferrule and the opposite end of said ferrule for limiting travel of said ferrule away from said adjustable stop against the bias of said spring means, a diaphragm engaging said one end of said ferrule and cover means surrounding said one end of said ferrule and the opposite end of adjustable stop and defining a chamber enclosed by said diaphragm and subjected to the pressure in said mixture conduit downstream of said throttle, whereby when said pressure is below a selected level said diaphragm may displace said ferrule and said plunger against the bias of said spring means to engage said ferrule with said stop means and to move said link in said slot to provide an enriched air-fuel mixture, whereby when said pressure is above said selected level said spring means may displace said ferrule, said diaphragm and said plunger to engage said ferrule head with said adjustable stop and to move said link in said slot to provide a lean air-fuel mixture, and whereby said air-fuel mixtures may be adjusted by removing said cover means and said diaphragm to expose said one end of said ferrule and said opposite end of said adjustable stop, by adjusting the position of said adjusting screw relative to said ferrule, and by adjusting the position of said adjustable stop relative to said wall.
 1. A carburetor comprising a mixture conduit having an air inlet and a mixture outlet, a throttle disposed in said mixture outlet for controlling flow therethrough, an air valve disposed in said air inlet for measuring air flow therethrough, a fuel passage entending to said mixture conduit for supplying fuel thereto, a metering orifice disposed in said fuel passage, a metering rod disposed in said metering orifice for controlling fuel flow therethrough, a lever positioning said metering rod, a link extending from said air valve to said lever for moving said lever and said metering rod to control fuel flow through said metering orifice in accordance with air flow through said air inlet, said lever having a slot receiving said link, and means for varying the position of said link in said slot to vary the travel of said metering rod in said orifice for selected movement of said air valve, said means including a reciprocable plunger connected to said link, a ferrule surrounding said plunger, said plunger having an adjusting screw received in one end of said ferrule for varying the relative positions of said plunger and said ferrule, a wall, an adjustable stop supported in said wall and surrounding said ferrule, said ferrule having a head engageable with one end of said adjustable stop, spring means biasing said head into engagement with said end of said adjustable stop, stop means engageable with the opposite end of said ferrule for limiting travel of said ferrule away from said adjustable stop against the bias of said spring means, a diaphragm engaging said one end of said ferrule and cover means surrounding said one end of said ferrule and the opposite end of said ferrule for limiting travel of said ferrule away from said adjustable stop against the bias of said spring means, a diaphragm engaging said one end of said ferrule and cover means surrounding said one end of said ferrule and the opposite end of adjustable stop and defining a chamber enclosed by said diaphragm and subjected to the pressure in said mixture conduit downstream of said throttle, whereby when said pressure is below a selected level said diaphragm may displace said ferrule and said plunger against the bias of said spring means to engage said ferrule with said stop means and to move said link in said slot to provide an enriched air-fuel mixture, whereby when said pressure is above said selected level said spring means may displace said ferrule, said diaphragm and said plunger to engage said ferrule head with said adjustable stop and to move said link in said slot to provide a lean air-fuel mixture, and whereby said air-fuel mixtures may be adjusted by removing said cover means and said diaphragm to expose said one end of said ferrule and said opposite end of said adjustable stop, by adjusting the position of said adjusting screw relative to said ferrule, and by adjusting the position of said adjustable stop relative to said wall. 